ALBERT

Description: In addition to seismically mapped fault structures, a large number of faults below the limit of seismic resolution contribute to subsurface deformation. However, a correlation between large- and small-scale faults is difficult because of their strong variation in orientation. A workflow to analyze deformation over different scales is described here. Based on the combination of seismic interpretation, coherency analysis, geostatistical analysis, kinematic modeling, and well data analysis, we constrained the density and orientation of subseismic faults and made predictions about reactivation and opening of fractures. We interpreted faults in seismic and coherency volumes at scales between several kilometers and a few tens of meters. Three-dimensional (3-D) retrodeformation was performed on a detailed interpreted 3-D structural model to simulate strain in the hanging wall at the time of faulting, at a scale below seismic resolution. The modeling results show that (1) considerable strain is observed more than 1 km (0.62 mi) away from the fault trace and (2) deformation around the fault causes strain variations, depending on the fault morphology. This strain variation is responsible for the heterogeneous subseismic fracture distribution observed in wells. We linked the fracture density from the well data with the modeled strain magnitude and used the strain magnitude as a proxy for fracture density. With this method, we can predict the relative density of small-scale fractures in areas without well data. Furthermore, knowing the orientation of the local strain axis, we predict a fault strike and opening or reactivation of fractures during a particular deformation event. Tina Lohr graduated in geology at Freiberg University, Germany. She is currently completing her Ph.D. at the GeoForschungsZentrum (GFZ) Potsdam. As a Marie-Curie fellow, she joined the Fault Dynamics Research Group at the Royal Holloway University of London for 5 months. Her research is focused on seismic interpretation, fault analysis, and structural restoration and modeling. Charlotte Krawczyk is now at the Leibniz Institute for Applied Geosciences and is a professor for geophysics, with focus on seismics at Technical University Berlin. From 1995 to 2007, she was a senior scientist at GFZ Potsdam. She did her Ph.D. at GEOMAR, Research Center for Marine Geosciences, Kiel, and received her diploma in geophysics from Kiel University. David Tanner earned his B.Sc. degree at Liverpool University (1988), his M.Sc. degree at Imperial College, London (1989), and his Ph.D. at Giessen University, Germany (1995). His main research interest is three-dimensional structural and geometrical modeling of seismic and outcrop data at all scales. Ramin Samiee received his M.S. degree in geology at Heidelberg University and his Ph.D. at Erlangen University (1998) in Germany. His interests are facies and diagenesis of carbonates and siliciclastics, log analysis, and seismic interpretation. He worked as a consultant for Shell, PanTerra, BEB, and Trappe Erdoel Erdgas Consultant (TEEC) and is now at RWE Dea AG. Heike Endres received her diploma in geophysics in 1995 from Muenster University, Germany. She worked as a geophysicist for Western-Geco and TEEC. For this project, she was part of the working group of RWTH Aachen University. Peter Thierer received his diploma in geology from Kiel University, Germany, in 2001. He worked as a research associate at GEOMAR Research Center for Marine Geosciences, and, since 2006, for TEEC. Onno Oncken received his diploma and Ph.D. at Cologne University, followed by postdoctoral research at Muenster and Frankfurt Universities, and a professorship for structural geology at Wuerzburg University. In 1992, he joined the GFZ in Potsdam. He is the director of the Geodynamics Department and holds a faculty position at Free University Berlin. Henning Trappe received his Ph.D. from Kiel University, Germany, in 1986. He worked at BEB from 1986 to 1992 as a geophysicist. Since 1992, he is the head of the self-founded TEEC and TEECware. Raik Bachmann received his diploma in geology from Freiberg University, Germany. Presently, he is finishing his Ph.D. at GFZ Potsdam and Free University Berlin. His work focuses on exhumed convergent plate boundaries and fossil seismicity. Peter Kukla graduated in geology from Wuerzburg University, Germany, and received his Ph.D. from Witwatersrand University, South Africa. His professional career included positions at Witwatersrand University (1986–1990), Shell International Exploration and Production (1991–2000), and RWTH Aachen University (since 2000) as a full professor of geology, head of the department, and director of the Geological Institute, with research focus on petroleum reservoir geology.